Area Forecast Discussion
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869 FXUS62 KTAE 271408 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1008 AM EDT Sat Sep 27 2014 .Near Term [Through Today]...
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The 8 am EDT regional surface analysis showed a developing, quasi- stationary front off the FL Panhandle coast to the central Gulf of Mexico, and a high pressure ridge along the Piedmont. Vapor imagery and upper air data showed increasing deep layer moisture along the Gulf Coast, as this region was embedded in southwest winds aloft- in between an unusual, broad, "double barrel" low over the central CONUS, and a ridge near the U.S. east coast. Our latest PoP forecast for this afternoon, a blend of our previous forecast and our latest ensemble of Convection Allowing Models (ECAM), has the highest PoP (50%) around Cross City, and the lowest PoP (10%) from Dothan to Albany. Based on the thick cloud cover and 8 am EDT sounding from Tallahassee, we trimmed back our high temperature forecast slightly to the lower 80s. Recent buoy observations and high-resolution NWP guidance showed Small Craft Advisory conditions across portions of our coastal waters at 9 am EDT, so we issued an advisory through 2 pm EDT.
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&& .Aviation...
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[Through 12Z Sunday] As has been the case the past several days, a fairly solid deck of low cigs developed across our entire forecast area this morning. We expect cigs to slowly lift from the current low-end MVFR levels to VFR levels early this afternoon. MVFR cigs are likely to return overnight, along with increasing rain chances (especially around KECP).
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&& .Prev Discussion [353 AM EDT]...
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.Short Term [Tonight Through Monday]... The main concern is the potential for heavy rainfall across the area and the potential for flash flooding. The GOES blended TPW shows a large area of precipitable water values over 2 inches across the Florida peninsula and stretching into the Gulf. This has also been sampled by the 00z Tampa sounding which had an impressive PWAT of 2.38 inches. As an upper trough approaches from the west on Sunday into Monday, this deep moisture will be pulled northward. In addition, a weak area of low pressure may develop along the Gulf coast on Sunday and lift northeastward on Monday, further enhancing low level convergence across our western counties, especially near the coast. Some of our local WRF runs are quite bullish on rainfall amounts along the panhandle coast. The very high totals seen on some of those runs may be a bit suspect due to overdeveloping the area of low pressure, but the large scale ingredients for some heavy rainfall look fairly favorable. In fact, the GFS ensemble mean precipitable water forecast for Sunday through Monday is up around the 99th percentile in terms of the model climatology (M-climate) for this time of year, which is impressive and by definition doesn`t happen very often. With this tropical airmass in place and some synoptic forcing in the area, heavy rain wording was used for the western half of the forecast area. A flash flood watch was considered, but with the main event not expected to be until Sunday into Sunday night, confidence was not quite high enough in the heaviest rainfall amounts to issue a watch this early. With the dry summer, flash flood guidance values are not particularly low either at the moment. Therefore, it seemed prudent to wait for the event to get a little closer and more into the range of the hi-res guidance ensemble to make a decision on any watches. .Long Term [Monday Night Through Saturday]... As the surface low and upper trough shift to our east Monday night into Tuesday we will see a gradual decrease in deep layer moisture along with significantly lower rain chances through the remainder of the week. Expect temperatures to run near or just above normal. .Marine... Northeasterly flow will shift to easterly today and become southerly by Monday ahead of a weak area of low pressure. Exercise caution conditions will likely continue across most of the area today. Somewhat elevated winds of 10 to 15 knots are expected for Sunday and Monday, but rather stormy conditions are also likely during that time with locally higher winds and seas near thunderstorms. A decrease in winds and seas is expected for next week. .Fire Weather... As we transition to a very wet pattern, there will be no fire weather concerns through at least early next week. .Hydrology... General rainfall amounts of 1 to 3 inches are likely across the forecast area through Monday, except 3 to 4 inches with locally higher amounts around 6 inches possible in a short period of time along the panhandle coast. These amounts are not expected to result in any river flooding due to low flows from the recent dry summer, although rises are certainly expected. However, isolated instances of flash flooding cannot yet be ruled out for Sunday into Monday, mainly along the panhandle coast and in the typically vulnerable urban and low-lying areas. If confidence continues to increase in this scenario, then a flash flood watch could be issued as early as this afternoon for Sunday.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 83 72 84 71 86 / 30 50 80 70 70 Panama City 82 73 81 74 85 / 30 70 90 70 70 Dothan 82 69 81 69 84 / 10 60 90 70 60 Albany 83 69 84 69 85 / 10 40 80 70 70 Valdosta 81 71 86 70 85 / 20 30 60 60 70 Cross City 83 71 86 70 86 / 50 40 60 60 70 Apalachicola 80 75 83 75 84 / 30 70 90 70 70
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&& .TAE Watches/Warnings/Advisories...
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FL...None. GA...None. AL...None. GM...Small Craft Advisory until 2 PM EDT this afternoon for Coastal waters From Ochlockonee River to Apalachicola FL out to 20 NM-Coastal waters from Apalachicola to Destin FL out 20 NM- Waters from Suwannee River to Apalachicola FL from 20 to 60 NM-Waters from Apalachicola to Destin FL from 20 to 60 NM.
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&& $$ NEAR TERM...FOURNIER SHORT TERM...DVD LONG TERM...BARRY AVIATION...FOURNIER MARINE...DVD FIRE WEATHER...HARRIGAN HYDROLOGY...DVD

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